If the pH of a solution is 3.5, what colour will be shown by each of the following indicators in the solution?
a)Methyl Violet
b) methyl red
c) Methyl orange
d) phenolphthalein
My answers:
a) Yellow to Blue
b) Red to Yellow
c) Red to Yellow
d) close to a light pink almost colourless.
I don't believe you have interpreted the question correctly. For example,
for methyl red at pH 3.5. I look in my text and I see MR changes in the range of 4.2 to 6.3 (R-Y); below pH 4.2 it will be red and above 6.3 it will be yellow. Therefore, I would answer that at pH = 3.5 MR would be red.
To determine the color shown by each indicator in a solution with a pH of 3.5, you need to understand the pH ranges in which these indicators change color. Here are the pH ranges for the given indicators:
a) Methyl Violet: Methyl Violet changes color over a pH range of 0.1 - 1.6. In this pH range, it transitions from yellow to blue. Since the solution has a pH of 3.5, Methyl Violet will not change color in this solution. Therefore, the color shown by Methyl Violet in the solution with a pH of 3.5 will be its initial color, which is yellow.
b) Methyl Red: Methyl Red changes color over a pH range of 4.4 - 6.2. In this pH range, it transitions from red to yellow. Since the solution has a pH of 3.5, Methyl Red will not change color in this solution. Therefore, the color shown by Methyl Red in the solution with a pH of 3.5 will be its initial color, which is red.
c) Methyl Orange: Methyl Orange changes color over a pH range of 3.2 - 4.4. In this pH range, it transitions from red to yellow. Since the solution has a pH of 3.5, Methyl Orange is within its color-changing range. It will therefore show a color between red and yellow, which is typically orange.
d) Phenolphthalein: Phenolphthalein changes color over a pH range of 8.2 - 10.0. In this pH range, it transitions from colorless to pink. Since the solution has a pH of 3.5, Phenolphthalein will not change color in this solution. Therefore, the color shown by Phenolphthalein in the solution with a pH of 3.5 will be its initial color, which is close to colorless, typically appearing as a very light pink.
So, to summarize:
a) Methyl Violet: Yellow
b) Methyl Red: Red
c) Methyl Orange: Orange
d) Phenolphthalein: Close to colorless, typically light pink.